Control for electric motors



0. F. SHEPARD.

CONTROL FOR ELECTRIC MOTORS.

APPLICKTION FILED'MAR. 2, 1917.

2 SHEETS-SHEET I.

Swumdoz 0, F. SHEPARD. CONTROL FOR ELECTRIC MOTORS. APPLICATION FILED MAR. 2|1911.

1,390,259. A r PatentedSept. 6,1921.

2 SHEETS-SHEET 2- awuemtoz XWM UNITED 3 STATEASF PATENT OFFICE.

OSCAR F. SHEPARD, OF CINCINNATI, OI-IIO, ASSIG-NOR TOTHE' WARNER ELEVATOR MFG. COMPANY, OF CINCINNATI,

OHIO, A CORPORATION OF OHIO.

CONTROL FOR ELECTRIC MOTORS Application filed March 2,

To all whom it may concern Be it known that I, OSCAR F. SHEPARD, a citizen of the United States, and residing at Cincinnati, in the county of Hamilton and State of Ohio, have invented a new and useful Improvementin Controls for Electric Motors, of which the following specification is a full disclosure. I

The invention relates to a system of mo-. tor control,-including certain improvements in controller devices of the magnetic rheostat type for an automatic governing of sequential performances beyondv a direct man ual control, so that the system i whenem-' ployed for elevator, service possesses safety qualifications. I i x 7 The invention inpart embraces and includes features and advantages disclosed in a prior patent to me, No. 986,952, dated Oct. 12, 1909, for controller for electric m0 tors, so that the various'objects of the invention expressed in said patent apply equally herein. 7 i x p In said prior patent, however, the various magnetic rheostat switch or controller. devices were each of aretarding or time. limit type, while in the system herein a single magnetic mechanicaltimelimit or retarding switch device is the primary governor switch controlling the operation of the various magnetic rheostat switches and other operative deviceswherein the different controlling stepsmust follow scriatim and all? tomatically for starting or stopping, forward or-reverse, low and high speeds, and beyond any direct manual control.

Therefore principally, the object of the invention is to provide a time limit and retarding switch device, for, making and breaking a series of electric circuits scriatz'm for various motor controlling results.

Another object of the inventionis to pro vide a switch device moving under a time or retarded motion, in which the retarded ino tion in one direction results from a mag netic resistance or influence upon the moving part. i i

The invention also contemplates certain novel features of the construction and combinat-ions and arrangements of the several parts of the improved controller, whereby certain important advantages are attained and the device is rendered simpler, cheaper Specification of Letters Patent. Patented Sept. 6, 1921 1917. Serial No. 151,889.

and otherwise better adapted and more convenient tonnes, and whereby precaution is afforded against damage due to carelessness and inexperlence on the part of the operator, as will be hereinafter fully set forth.

Drawlngs depicting the invention are herewith included and form a part of this specification, in which like characters of ref erence denote corresponding parts throughout theseveral views, of which Figure l is a diagrammatic view of the system.

Fig. 2 is a sectional view, partly in elevation of the time limit switch device.

Fig. 3 is a section on line 3 3, Fig. 2.

Fig. 4 is an enlarged side elevation of the coupllng connecting two alined' shafts of electric motor controlling and reversing switches, withone of the shafts showing in section.

Figs. 5 and 6 are diagrammatic views, illustrating modified motor controlling systems.

Fig. 7 is an elevation of the switch device shown in Fig. 2. T

Referring to Fig. 1, 1 indicates a switch board supporting a main switch constituting a shaft-'6 mounted to rock between a series the duplicate of one another arranged in alined electrically connected sets, so that the same electric circuit connections are made and established by the switch elements ,7 and 8 in either of their alternate switch closing positions. The switch elements when neutral are sustained by their shaft in an intermediate position between the upper and lower series ofcontacts.

. 23 indicate the respective terminals of the feed or supply circuit with terminal 2 connected with the contact 4 one of the upper series of contacts and terminal 8 with the contact 5 a second of the upper series of contacts. Contact 4 of the upper series is in electric connection with contact 4 of the lowers'eries, and likewise contact 5 ofthe upper series is in electric connection with contact 5 of the lower series. The contacts e l-42 and 5-5 of the upper and lower series or groups are directly opposite each other respectively, so as to adapt them to be en gaged by the respective switch elements of shaft 6 when rocked in either direction from the central position whereby an electric communication is established from terminal 2 to the element 7 when engaged with either of the contacts 4-4: and similarly when element 8 is engaged with either of the contacts 5-5, communication is established with terminal 3. Adjacent to contacts 1 1 of the upper and lower series, upper and lower contacts 99 are provided, adapted alternately to be engaged with the switch element 7 for establishing electric communication from a contact 41 across switch element 7 with contact 9 of either the lower or upper series depending upon the position of switch element 7. Likewise a second set of upper and lower contacts are provided adjacent to contact 55 adapted to be strapped across by the switch element 8. Upper and lower contacts 9-9 are in electric connection similar to contacts 41-4. Likewise upper and lower contacts 1010 are in electric connection. The switch elements 7 and 8 thus strap across two contacts to complete a circuit between the contacts either of the upper or lower group.

The movable switch elements 7 and 8 and their respective contact form a primary switch device for controlling the electric energy to the various devices of the system.

Primary switch operating mechanism.

The main switch shaft 6 is operated or rocked by electrically actuated mechanism comprising two solenoids 11 and 12 mounted side by side upon the switch board 1, each having a core member 13 adapted to fall to a lower position by gravity when the respective solenoids are deenergized. The lower end of the cores are each provided with a notch for engagement with an arm of a lever 14 fixed to the shaft 6. The lever 14 has two arms oppositely divergent and inclined downwardly, one arm to engage with the core of solenoid 11 and the other with the core of the solenoid 13. By this construction andarrangement, when both solenoids 11 and 12 are deenergized or neutral their cores will drop by gravity, or pressure, in a retracting direction to move the shaft 6 to a central or intermediate position, neutralizing the switch elements 7 and 8. hen one of the solenoids, for example solenoid 11, is energized, its core 13 will be raised, mowing the lever 14 and shaft, to rock the shaft to its full extent in one direction,

bringing the switch elements 7 and 8 into engagement with the appropriate switch contacts of the upper and lower series depending upon the control desired to be established for a forward and reverse motor drive.

For controlling the operation of the switch actuating device a pilot or manually operated switch is shown at 15. This pilot switch comprises a plurality of stationary contacts mounted upon a suitable base and arranged in two groups and within the arch swing of a switch lever 16, to be engaged by said lever. The two groups are'in a spaced relation upon opposite sides of a central radial line of the lever 16, one group for a forward control and the second for a reverse control, and each group includes separate contacts for slow and high motor speed re sults.

The motor controlling system, shown in Fig. 1, is principally contemplated for elevator service, wherein the switch mechanism 15 is mounted within the cab or car of the elevator, for manually starting and stopping the car in an up or down direction.

The contacts at the right designated by D are for the reverse or downward starting and "speed control and the contacts at the left designated by U are utilized for the up ward and forward starting and speed control. The switch 15 controls the circuits to the solenoids 11 and 12 for actuating the main switch devices mounted upon the switch board 1. Solenoid 11 has its winding in connection with contact 17 of the U group of contacts of the pilot switch device 15 through a conductor 18 connecting with the solenoid 11 and contact 17, thus representing the upward or forward motor control for moving the shaft 6 in an appropriate direction. Solenoid 12 has its winding in connection with a contact 19 of D group of contacts of the pilot switch 15 through a conductor 2O connecting with the solenoid 12 and contact 19 for energizing the solenoid 12 for moving the shaft 6 in a direction alternate or reverse from shaft moving influence of solenoid 11.

The lever 16 of the pilot switch device 15 serves as a strap to connect certain contacts of one group in electric connection with certain contactof the second group. The function of each group of contacts are similar to one another excepting as to the forward and reverse control, and therefore some of the contacts may be regarded as common to both groups. Therefore, a description of one will answer for both wherein the function is a common one for the control of the common devices.

Therefore, the description will be directed to the D group of contacts, assuming that the switch lever is moved to the right to be engaged respectively with such contacts in following the different steps or performance.

Group D besides the contact 19 contains a contact 21 for starting and slow speed results, and a third contact 22 spaced from contact 21 for car motion accelerator-y results.

The contact 21 connects through a conductor 28 with the contact 5 of energy supply terminal 3, and with the switch lever 16 engaged or bridged to connect the contacts 19 and 21 completes a partial circuit from the terminal 3 or contact 5 througheonductor 23, contact 21, switch lever 16, contact 19, conductor 20 to solenoid 12. p

The opposite pole of the winding of the solenoid 12 connects with a conductor 24, (conductor 21 extending downward at the right of Fig. 1). A branch conductor 25 connects with conductor 24, having its opposite end connecting with a contact of a time limit magnetically controlled switch. This switch deviee' will be hereinafter described'in detail, and for the present let it be assumed that a circuit branch through said time limit switch device is complete with branch conductor line 25, and a conductor 25 having one end connecting with a contact plug 63 at the upper end of the time limit switch device. The oppositeend of the conductor 25 connects with a switch termi nal of a magnetically controlled switch device G. From an opposite switch terminal of the magnetically controlled switch device G, a

, conductor 26 connects with the contact 1 of energy supply terminal 3. r i I The magnetically operated switch device G normally has its magnet g deenergized so that its circuit controlling switch element closes or connects the switch terminals of conductors 25 and 26. Under-such conditions a partial electric circuit is complete from supply terminal 2 or contact 4L- through conductor 26, switch Gr, conductor 25, through time limit switch device and conductors 25 and 2 l to" the "winding of the solenoid 12, and whenever the switch lever 16 connects contacts 19 and 21 the circuit is completedwith solenoid 12 to influence its core piece or plunger 13 for rocking the shaft 6. The main circuit line just described connecting the winding" of solenoid 12 with th terminal line 2 serves similarly to and is common for the winding of the solenoid 11, and completes one partial circuit for the winding of said solenoid "11 as a negative line. The opposite windingpole of'solenoid 11 connects with a conductor 18, which con ductor connects at its opposite end with contact 17 ofthe pilot switch 15.

Contact 17 is an element of the U group and said group likewise contains contact 21' and 2 the duplicates of contacts 21 and 22 of the D group. Thus when switch lever 16 connects contact 17 and 21 of the U group it willcomplete an electric circuit with the windings of solenoids 11 energizing said solenoid to raise its core plunger 13 for a reverse motion of shaft 6 from that immaintaining a break insaid last mentioi i parted to it by the movement of plunger 18 of the solenoid 12. Thus the first step upon throwing the pilot switch lever 16 either to the right or left depending upon the direction of car motion desired, is to operate either solenoid 11 or 12 for throwing the switch elements 7 and 8 in an appropriate direction and thus operating the primary switch devices controlling the circuit to the electric motor.

Electrically ope rated renaming switch.

I The panel board 1 supports a switch device having movable contact elements operated by the shaft 6 which comprises a shaft 28 connecting with shaft 6 through a compensating connection 29. The connection 29 as shown in Fig. 4 comprises a pin or projection 30 on the main shaft (3 engaging into a slot or notch in the connection or collar 29 secured to shaft 28. The pin alter nately engaging the shoulders 3132 within the'collar, depending upon the direction of rotation of shaft 6. This form of connection provides for a certain degree of free movement or play between the shoulders so that the reversing switch shaft 28 is operated and rocked in unison with the main shaft 6, but to a lesser extent, enabling the reversing switch shaft 28 to lag behind the main switch shaft 6 to an extent such that the switch arms or elements Sift-8a of the reversing switch remain in connection with their respective stationary contacts of either the upper or lower series until the main shaft 6 has been rocked to its central position with its switch elements '7 and 8 midway between their respective upper and lower contacts 1, 9, 10 and 5. f

This difference of time of breaking of the switch elements 7 and 8, and reversing switch arms 333 1, is for the purpose and advantage previously recognized and described in my aforesaid prior patent, principally for preventing a motor reversal or quick retarding before the motor has come to rest. The lag permits the switch arms 33-34 of the main reversing switch to re main in communication with their respectively engaged contacts or terminals until the main switch shaft #6 has moved its switch arm or main circuit controlling switch elements to a. central or neutral position. This maintains a shunt held '0 nnection with the armature of the motor and a. current flow in the shunt field due to the dynamic action of the armature and netic inertia of the field until the motor comes to rest. Such current flow controls the switch G, which switch in turn controls the circuit to a time limit switch device Cl circuit for a return interval of said time limit switch to its normal or starting position, so that after once starting, it is impossible for the operator to reverse or restart until the motor shall. have come to rest. The switch arms are insulated from the shaft 28, and thus are separate from one another so as not to establish communication between each other. Switch arm 33 is adapted to engage alternately with the two contacts 3536 of the upper and lower series, and switch arm 34 alternately with the contacts 37 and 38 of the upper and lower series. Contact 35 and 38 are cross connected by a conductor 39 and contacts 36 and 37 are cross connected by a conductor 40. The arm 33 is in connection with contact 16 by a conductor 41 and the arm 34 connects by a conductor 42 with the field windings 43 of the motor 44. Contact 38 connects with a conductor with one pole of the armature 46 and contact 36 connecting with a conductor 47 leading to and connecting with the opposite pole of the armature 4-6.

Therefore, the switch arm 33 serves to alternately complete a partial circuit from the supply terminal. 3 to the armature 46 through either conductor or conductor 47 depending upon which of the contacts 35 or 36 it engages, to make the circuit flow in opposite or reverse directions. Thus assuming that the switch arm is engaged with contact 35 a partial circuit will be completed from the terminal supply line 3 through contact 5, switch element 8 contact 10 of both contacts 10 of both upper and lower series, conductor 41. through switch arm 83, contact 35, conductor 39, contact 39, conductor 45, to one pole of the armature windings of the armature 46. With the switch arm thrown into opposite directions to engage with contact 36 a partial circuit will be completed from the supply terminal 3 through contacts 5 of the upper and lower series, switch element 8, contact 10, conductor 41, switch arm 38, contact 86, onductor 47, with the opposite pole of the armature windings of armature 46. The return circuit is through automatically controlled switch devices to be hereinafter de scribed for both the return lines of the different field windings and armature windings. The various parts heretofore described, with the exception of the magnetic controlled time limit switch, is substantially the same as disclosed and described in my aforesaid prior patent so that further detail elab-.

oration need not be made herein.

Tel 272 c limit magnetically operated switch.

This switch represents one of the essential features to the system and provides a device beyond the control of the operator for gradually making and breaking various partial circuits for controlling magnetically operated switch devices for rheostat regulation so as to gradually out out a starting resistance in series with the motor windings,

from the cylinder.

for motor speed acceleration, making it impossible for the operator to speed the motor under any sudden influence and thereby pre vent injury to or an overloading of the motor. It is therefore, immaterial whether the operator in controlling the switch 15, immediately upon starting moves the switch lever into connection withthe high speed contacts, as the speed acceleration is beyond his control.

The time limit switch comprises a solenoid magnetic winding 49, wound upon the spool 50. The bore of the spool 50 concentrically contains a tube 51 which projects beyond the upper end of the spool and through the magnet frame 52. The magnet frame 52 is suit ably anchored to a supporting panel by means of bolts 53. 54 indicates an armature core plug engaged into the core of the spool and secured to the magnet frame 52. The armature core plug 54 has a conical upper end to increase its area and increase the pull of the magnet. An air duct 55 extends longitudinally through the core plug 54 and magnet frame 52 for the escape of air from the chamber formed between the plug 54 and end of the armature plunger 56. The armature plunger 56 has its lower end recessed correspondingly to the contour of the conical end of the plug 54 to meshingly engage with the plug when the magnet is energized. The armature plunger 56 pro jects upwardly within and beyond the tube 51 and is provided with a flanged end to form a shoulder for the coil spring 57 oncircling the plunger. The lower end of the spring 57 seats against the magnet frame 52 and urges the plunger upwardly when the magnet is deenergized.

Upon the upper end of the armature 56 rests a cross shaped piston arm 58, connected to a piston 59 slidably mounted within a dash-pot cylinder 60. The upper end of the cylinder 60 is closed by a head 61 and is cireumferentially recessed to receive the mag net winding 62 which winding is insulated A flanged insulator bushing 62 extends through the cylinder head 61 to receive and insulate a contact plug 63 projecting into the cylinder. The lower end of the plug 63 is interior of the cylinder and engages a flexible contact member 64 fixed upon the end of the piston, when the piston is in its uppermost position.

A pair of contact rollers 6566, are each dependingly supported from a cross lug 67 of the piston arm 58 by links 68, pivoted upon the cross lug 67. A spring 69 is interposed between the opposite links 68 respectively carrying the rollers 6,566, for urging the links outward in a direction apart from each other, yieldingly engaging the contact rollers against the respective contacts of a series of contacts arranged in vertical tiers in the path of the contact roller travel. The rollers being drawn across the contacts by the plunger 56 which reciprocates, being forcibly moved in one direction or upward by a spring 57 and moves in the opposite direction or descends by gravity. The descending motion of the armature plunger 56 is interrupted for a brief interval at the cutting out of a section of resistance and before the motor reaches its maximum rate of speed for the resistance reduction, owing to an effective increase in excitation of the magnet windings 62 during the interval causing a magnet pull suflicient to overcome the weight of the gravity descending plunger 56.

These contacts 70, 71, 72, comprise a series of contacts of the tier at the left side to be engaged by the roller 65 and four contacts 73, 74, 75 and 76, a series of contacts of the tier at the right side to beengaged by the roller 66. The contact for either the right or left series are secured upon an insulator support 77 suitably secured to a base or panel board.

As shown in Fig. 3, the piston arm 58 at its rear edge has oppositely projecting lugs 78 engaged between the insulator guide strips 79 for properly guiding the piston arm in its reciprocating motions.

The contacts at the left are arranged to present a relatively staggered relation from those at the right, thus offsetting their ends so that one roller may remain in engagement while the opposite roller moves from one contact to a second, and the spacing of the contacts of each series is of such a degree that the roller engages a second before leaving or breaking from the first.

The foregoing described device provides a time limited or retarded magnetic operated switch, whereby the motion of the moving switch parts are timed to afford asuflicient interval between successive resistance variations so that no damage can result to the machine under control, and in which the control is electro-mechanical beyond any direct manual control.

Rheostat magnetically operated switch device.

As shown in Fig. 1 of the drawings, seven magnetically operated switch devices are provided, divided into upper and lower groups, four of which comprise the upper group designated respectively as a, b, c, and d, and three the lower group, designated as E, F and G. Each switch device of the upper group includes a magnet winding and a swinging armature, as a switch element, and each of the lower group includes a magnet winding and bell crank shaped armature lever as a switch actuating element, each carrying switch blocks 80, 80 80" respectively, for cooperating with stationary Switch contacts. The construction of these switch devices of either group may be of any type of construction most serviceable and efficient to produce the results desired 1 vices a, b, c .and d are arranged for successive operations to control the starting resistance sections 81, 82 and 83, together with a field winding of the motor. Of the lower group switch device E shunts the current from the magnet of the switch device F until starting resistance is out out, the switch device F being controlled by pilot switch 15 to'cut in resistance in the motor shunt field for high speed and the switch device G in the shunt field circuit, is held down until motor stops and controls the time limit switch device so that a second operation cannot be started until the time limit switch device hasreached a limit of throw.

The grouping arrangement and number of magnetic switch devices may be raised to conform to various modifications and the arrangements of resistance sections as is exemplified in the modification of motor controlling system, shown in Figs. 5 and 6 in which the time limit switch device is the essential feature in the control, making it obvious that many of the elements of the system, shown in Fig. 1, may be dispensed with without departing from the principles of the invention. a

Rheostwt wiring diagram, shown in Fig. 1.

The description of the wiring diagram will follow in seriatz'm, the operations of the various switch elements or devices of the system, embraced in the upper groups a, b, c, d, and those of the lower groups E, F and G.

Now again assuming that the pilot switch lever is thrown to connect contacts 19 and 21 of the D group and that the solenoid 12 is energized and the parts influenced thereby operated as heretofore described for throwing in the supply circuit into the controlling system, as the first step in the operation bringing the various movable switch arms or. elements mounted upon shaft 6 and 28 into engagement with their respective contacts of the upper series upon the panel board 1.

Such first step, as a motor starting step completes the motor circuit from the terminals 2 and 3 through the following course. Starting from the plus terminal 3, through contact 5, switch element 8, contacts 10 and 10, of both upper and lower series, conductor 41 to reversing motor switch, switch arm 33, contact35, cross conductor 39, lower contact 38, then through conductor 4-5 to motor armature 46, armature windings, conductor 47, contact 36, cross conductor 40, contact 37, switch arm 34, conductor 42, to a series field windings 43 of the motor 44'. From the opposite terminal of the motor field winding 43, through a conductor 84, connecting at the right terminal of the resistance sec tion 83, 82, 81, through said sections 83, 82, 81, to the left resistance terminal. A conductor 85 connects with the left resistance terminal and extends to the right to connect in series with the dash-pot magnet windings 62 of the time limit magnetically operated switch. Then from the oppositepole of the magnet winding 62, through a conductor 86, connecting with contact 9, 9, of the primary circuit controlling switch and then through the switch element 7 to contact 4 and main minus terminal line 2.

The magnet winding 62 of the magnetic retaining dash-pot is in series with the motor windings and motor starting rheostat sections 81, 82, 83, offer economy in the con sumption of energy, in fact, the consumption is inappreciable, as only a small number of winding coils are required to produce a sufficient coil excitation for properly retarding or timing the gravity descent of the dashpot piston and its switch elements. The time limit magnetic switch normally has its piston in its uppermost position with the rollers in engagement with the upper contacts 70, 73, and which position it occupies in starting.

In such uppermost position of the piston, a circuit is completed to the magnet windings49 of the dash-pot piston actuating solenoid. One terminal of said magnet or sole noid winding 49 connects with contact 70, through a conductor 87, and the opposite winding terminal through a conductor 88 in V arallel connection with the conductor line eading to the terminal of the dash-pot winding 62. The solenoid winding 49 can be said to be also in series with the winding 62 of the dash-pot, through the following circuit commencing at the supply terminal 3 Conductor 23, through pilot switch 15, conductor 20, solenoid winding 12, conductor 24, branch line 25, contact 73, the roller contacts 66, 65, depending from the dash-pot piston, contact 70, conductor 87, solenoid. winding 49, conductor 88, through dash-pot winding 62, conductor 86, to contact 9, 9,

switch element 7 contact 4, 4, and supply terminal 2.

This energizes the magnet 49, attracting its armature plunger 56, drawing it away from the stem of the dash-pot piston to permit the piston to descend by gravity but retarded in its motion by the magnetic influence due to existing winding 62.

Now let it be assumed that the dash-pot piston has descended toa degree to bring its contact rollers to a second position in which roller 66 is engaged with contact 74' and roller still engages with contact 70. This will complete the circuit to the magnet windin s of relay a of the rheostat controlling switched through the following course, and this may be said. to be in series with the magnet winding 49 for one partial circuit through contact 70, roller switch elements 65, 66, contact 74, conductor 89, to one terminal of the magnet winding a, then through conductor 90, connecting with the opposite ter minal of the magnet winding a, downwardly and around to conductor 24, joining conductor 24 at the conductor branch 25, leading to the contact 73. From the conductor 24, it continues through the solenoid winding 12, pilot switch 15, conductor 23 and plus terminal 3.

With the magnet Or relay a energized, it will attract its armature lever so as to bring the same into engagement with the switch terminal 91 at the left end of a resistance section, thus cutting out resistance section 81 by completing the circuit from the conductor switch terminal 91 to armature lever of relay a, conductor 92, to the left end of the resistance section 82.

Now assume that the piston has descended to bring its roller contacts into engagement respectively with contacts 71 and 74, in which position the magnet of relay 7) will be energized to attract its armature lever, the circuit to said magnet winding being through a conductor 93, connecting with contact 71 and extended to one terminal of the magnet winding of the relay 5, then through the magnet winding and a conductor 94 which connects with the conductor 87 and in series with the magnet winding 49 of the time limit or retarding switch device. With the parts in this position, relay (1 is still energized and its armature lever held closed because the electric circuit is still complete through its magnetic winding, as the same can be said to be in series with the winding of the relay 6 energized to cut out the resistance section 82 with the section 81.

Now assume that the rollers are brought to a position to engage contact 71 and con tact 75, the electric circuit with the magnet winding of the relay c will be complete so as to energize the same and attract its armature lever for cutting out the resistance section 83. In this, step relays a, 7) and c, are all active. Any number of resistance sections may bethus controlled by providing the re quired number of contact elements to be engaged sem'cz'm by the switch rollers 65, 66, and the wiring plan of such design to hold in circuit the previously operated relays.

After the contact rollers 65, 66 have moved to a position to engage contact 72 and contact 76, the relay (Z will be energized to completely cut out the series field winding of the motor, so that the motor is run as a simple shunt motor.

with the relay (Z energized or active, the wiring scheme is so arranged that the con- 'ductor lines 42' and 84lleading to the motor series field winding 43 is short circuited or cut out. It is accomplished by providing a Motor shunt field wiring.

One partial circuit of the motor shunt field wiring can be traced by commencing with energy supply terminal 3, then through either of the contacts 5, 5, of the main circuit controlling switch mechanism, switch element 8 either of the contacts 10, 10, conductor 41, conductor 96, which is shown as having one end connected to the terminal of the reversing switch lever arm 33. The con ductor 96 extends downward, then to the right, then downward again and continues to the left below the relays E, F and G, having in series therewith a shunted resistance 97 controlled by the switch armature lever of the relay F. From the shunted resistance 97, the line continues through 98 to the shunt field winding 99 of the motor 4,4.

It will be observed that the only break in the above described partial circuit of the shunt field line beyond the main circuit controlling switch devices actuated by shaft 6, is at the shunted resistance 97.

When the relay F is inactive the shunt field resistance 97 is short circuited or cut out by a branch conductor line connected around the resistance 97, comprising a conductor 100, connecting at the right terminal end of the resistance 97 at one end, and with a terminal switch element at its opposite end, the terminal switch element being adapted to be engaged by a switch block 80 mounted upon and insulated from the armature switch lever of the relay F. This switch block 80 engages with a second terminal switch element to continue the line through a conductor 102, connecting with said second switch element at one end.while the opposite end of said conductor 102, connects at the left terminal end of the resistance 97. Thus, whenever the magnet f is energized attracting its armature lever, the cut-out line will be broken, whence the circuit must flow through the resistance 97, the resistance, however, can not be cut out by the relay F until the relay E is active and the relay 15 does not become active until the pilot switch lever 16 is brought to engage with either the U or D high speed contact 22 or 22' respectively. The high speed results can not take place until the dash-pot piston has moved to its lowermost position bringing its contact rollers 65, 66, respec tively into engagement with he contacts 72, 76, and as the retarded motion of the clashpot piston is beyond the control of the operator, it can not be influenced by throwing the switch lever, immediately after starting, into connection with the high speed contacts 22, 22 until the serial step control orthe motor resistance cut-out has been accomplished.

The shunt field circuit is completed by a conductor 103 which connects with the ter minal of the shunt field winding 99, and em tends upwardly, then to the right in series with the magnet winding 9 of the relay G, then through conductor branch 104, which connects with conductor 88. From condoctor 88 it continues through the dash-pot magnet winding 62, conductor 86 to switch contacts 9, 9, of the main circuit controlling switch devices, which connect the contacts 9. 9, through switch element 7 with the supply terminal 2. As the relay can not be energized until the main circuit switch element is thrown into engagement with either of the upper or lower series of contacts, 4, 9, 10 and 5, and this makes it compulsory to operate the pilot switch after the dash-pot piston has reached its uppermost position, which position it must occupy before the circuit to either of the solenoids 11 and 12 can be completed, and to accomplish such operation, the relay G must also be inactive because it controls a partial. circuit leading to the solenoids 11 and 12. Thus the controlling steps must follow sem'ctc'm.

properly timed interval in its descent to complete the communication between contacts 7 2, 7 6, the electromagnet (a of the relay E will be thrown in series with the relays a, b, o, and (Z, and when the relay is energized, relay F will operate, breaking coromunication oi the shunt cross over lines or conductors 100.. 102. The relay (Z has partial. circuit conductor 101, connected to the contact 72, which is thrown in series with the magnet winding 0 of the relav E, through contact rollers 65, 00, contact 70. conductor 105, through magnet winding a of relay F), then through conductor 106 joining with the conductor leading to the magnet winding oi relay (2 and which, as before described, branches to connect with the contact 75.

Relay F controlling the shunt field, resistance 97 is in partial circuit with the pilot switch contacts to be controlled finally by the switch lever 16, but as its control is also dependent upon the control of the relay IE, it will be observed that two steps must be followed before a high speed result can be obtained.

First, the switch lever 16 of the pilot switch must be moved to engage with the contact 22 of the D group or the contact 22 of the U group, and the dash-pot piston must be moved to its lowermost position for completingthe circuit with the relay E. Contact 22 is connected by a conductor 108, leading to one switch terminal of the switch device, E, controlled by the armature lover of the relay 0, said armature lever being provided with a switch-block 30, adapted to ngage for closing a gap between the switch terminals of conductor 108 and conductor 107, the conductor 10? having a branch connecting with the conductor 23 and a second branch connects with the winding of magnet Likewise, conductor 108 has a branch connecting with the opposite end of magnet winding f. When the switch device E, controlled by relay 9 is closed the circuit will follow a path of least resistance by passing the magnet winding f of relay F, and when the switch mechanism E of the relay 0 is broken the switch device F will become active, moving its armature lever cutting in the resistance 97 oi the shunt field winding, permitting the motor to run at its highest speed.

In Fig. 5 I have shown a modified wiring diagram, illustrating the current limit switch, as applied to a simple motor control circuit, effective in first completing the circuit through a sectional resistance element in the motor circuit and functioning to consecutively cut out the resistance sections in timed intervals to build up the motor speed and to subsequently short circuit or cut out the series motor winding, peanitting the motor to run as a simple shunt motor.

The mechanism of the current limit switch is the same as previously described with the exceptions of the elimination of the contacts 63, 61, at the top 01 the dash-pot cylinder and the difference in the arrangement of the control contact, in this case, there is provided an elongated contact 110 and live shorter contacts 111, as shown.

Normally the armature, series motor field, starting resistance and the retarding dashpot coil 62 are connected in series, the circuit being as follows, line contact 3, switch lever 8, conductor 112, armature 16, conductor 113, series field 73, conductor 11 1, starting resistance 83, 82, S1, conductor 115 to upper contact 11 1, contact rollers 66, 65,

conductor 109, dash-pot coil 62, conductor 1116, switch. lever 7 to line contact 2. The solenoid 41.9 is connected in parallel by conductors 117, 118, the shunt motor field being also connected in parallel by conductors 11.9, 120, as branch lines from -conductors 117, 118.

As the dash-pot piston descends, the contact rollers 65, 66 connect the elongated contact 110 successively with each of the contacts 111, thereby cutting out the resistance sections 81, 82 and 83, one after the other, until the roller 66 engages the last contact 111, which is connected by conductor 121 to the conductor 113, leading from the motor armature 16 to the series motor field. This position of the roller 66 establishes a circuit as follows Line contact 3, switch lever 8, conductor 112, armature 16, conductor 113, conductor 121, lowermost Contact 111, contact rollers 66, 65, elongated contact 110,.conductor 109, dash-pot coil 62, conductor 116, switch lever 7 to line contact 2. It will be noted that this circuit cuts out or short circuits the series motor field and permits the motor to run as a simple shunt motor. However, it it is desired that the motor shall be maintained as a compound motor, the lowermost contact may be eliminated.

1n the diagram shown in Fig. 1, the winding 62 of the time limit magnetically operated switch is energized by the current through the motor armature and series fielding windings of a compound motor, while in the diagram, Fig. 5, after motor starting, the winding 62 is in circuit with the current flowing only through the armature, when the motor is converted to a simple shunt motor, to avoid making a break in the stationary contact member 110 or 135 engaged by the contact roller 65.

In Fig. 6, I have shown a similar arrange ment with the additional provision of means for preventing a second motor operation until the dash-pot piston is completely restored to normal position.

. In this form of control the method of cutting out the starting resistance, and also the cut-out of the series motor field when the dash-pot piston is in its lowermost position is practically the same as described in connection with Fig. 5. lVhen the piston is in its uppermost position, as shown, the motor circuits are the same as shown in Fig. 5, but when in any of its lower positions, the circuit from the rollers 65, 66, to coil 62 must pass through a branch circuit including the terminals 25, 126, of a switch device 11 and conductor 12?. The magnet winding ii 01 the switch H is connected in series with the solenoid 19 of the time limit switch and when the dash-pot piston is in its uppermost position, as shown, this partial circuit is established as follows Line terminal 3, switch arm 8, conductor 128 to winding 7L, conductor 129 to solenoid 419, branch conductor 130, conductor 131, to the upper contact 111 of the right hand series, rollers 66, 65, contact 132, conductor 133 to coil 62, conductor 13 1, switch lever 7 to line terminal 2. This circuit energizes the relay H to complete the branch circuit from the coil 62 to the contact 135 and also energizes the solenold 419.

lVhen the contact rollers 65, 66, move from their uppermost position, the partial circuit from the solenoid 49 to the line terminal 2 is completed from branch conductor 130, through conductor 136 to conductor 137, terminals 125, 126, conductor 127, coil 62, conductor 134, switch lever 7 to line terminal 2. This provides a control system which prevents a second motor starting operation until the time controlled switch is normalized.

Having described my invention, I claim:

1. The combination of an electric motor, a motor field resistance, an electro-magnet operated switch device controlling said resistance, a motor starting switch having a movable switch element controlling the circuit to said electro-magnet switch device, and electro-magnetic means having its magnet windings in circuit with the motor for energizing said windings, thereby retarding the resistance reducing movement of said switch element.

2., The combination of an electric motor, a plurality of automatic switches for automatically controlling resistance in the series field winding of the motor, an automatic switch for automatically controlling resistance in the shunt field winding of the motor, a movable element for controlling the circuit to said automatic switches scriatim, electro-magnetic means for retarding the the movement of said element in one controlling direction, and means for moving said element in an opposite direction.

3. The combination of an electric'motor, a plurality of switches for automatically controlling resistance in the series field winding of the motor, a switch device having a movable element for controlling the circuit to said plurality of switches serz'atim, 40

and electro-magnetic means having a mag net winding in series with the resistance and motor for retarding the movement of said switch element for a gradual reduction of resistance and motor acceleration.

4. The combination of an electric motor, a resistance divided into sections in circuit with the motor field windin s, a plurality of electro-magnet switches For controlling respective sections of said resistance, a switch device for operating said electromagnet switches seriatim in reducing the resistance, and magnetic means having its windings in series with said resistance and motor windings for retarding the resistance reducing control of said switch device.

5. The combination of an electric motor, a resistance divided into sections in circuit with the motor field windings, an electromagnet switch device operating for reducing the resistance in sections serially, having its magnet windings in series circuit with said resistance and motor field windings, said device provided with a movableswitch element for controlling said resistance in sections, whereby each reduction in resistance produces a magnet excitation interrupting the movement of said switch element for an automatic step control of resistance and gradual motor acceleration.

In witness whereof I hereunto subscribe my name, as attested by the two subscribing witnesses.

OSCAR F. SHEPARD.

Witnesses M. SMITH, L. A. BECK. 

